1. Technical Field
The disclosure belonging to the technological field of semiconductor memory relates to a semi-floating-gate device and its manufacturing method, and more especially, to a semi-floating-gate device with perpendicular channel region and its manufacturing method.
2. Description of Related Art
Semiconductor memory is widely applied in various electronic products. The requirements for construction, performance, and density of semiconductor memories in different fields are diversified. For instance, static random access memory (SRAM) has high random access rate and low integration density, while dynamic random access memory (DRAM) has high density and medium random access speed.
FIG. 1 shows a planar channeling semiconductor device, comprising: a source region 501 and a drain region 502 with the opposite doping type formed in the semiconductor substrate which can be made of monocrystalline silicon, polysilicon or silicon on insulator. In the semiconductor substrate 500, a channel region 601 of the device is formed between the source region 501 and the drain region 502, wherein the channel region 601 is an inversion layer formed in the semiconductor substrate 500 when the semiconductor device works. The doping region 509 with a high doping concentration is formed in source region 501, and the doping region 510 with a high doping concentration is formed in drain region 502, wherein the doping type of the doping region 509 and the doping region 510 is same to that of the source region 501 and drain region 502.
A first layer of insulation film 503 is formed above the source region 501, the channel region 601 and the drain region 502, and a floating gate opening region 504 is formed in the first layer of insulation film 503 on the drain region 502. A floating gate 505 used as a charge storage node is formed above the first layer of insulation film 503 and covers the channel region 601 and the floating gate opening region 504. The floating gate 505 has the doping type opposite to that of the drain region 502. The doped impurities in the floating gate 505 can be diffused into the drain region 502 through the floating gate opening region 504. A diffusion region 602 is formed due to the spreading of the impurities diffusion of the floating gate 505. Thus a p-n junction diode is formed between the floating gate 505 and the drain region 502 through the floating gate opening region 504 blew the floating gate 505.
A second layer of insulation film 506 is formed due to covering the floating gate 505 and the p-n junction diode structure. A control gate 507 above the second layer of insulation film 506 is formed due to covering and surrounding the floating gate 505 of the gate of the device 508 are formed on both side of the control gate 507. The semiconductor device further comprises the contactor of the source region 511, the contactor of the control gate 507, the contactor of the drain region 513 and the contactor of the semiconductor substrate 514 made of conducting materials, that are used to connect the source region 501, the control gate 507, the drain region 502 and the semiconductor substrate 500 with the external electrode.
To guarantee the function of the semiconductor device, the planar channeling semiconductor device needs longer channel length. But the unit area of semiconductor device will be bigger, and the chip density will be reduced. It will hinder the further development of chips towards miniature direction.